// Copyright (c) 1999-2004 Brian Wellington (bwelling@xbill.org)

package org.xbill.DNS.utils;

/**
 * A routine to produce a nice looking hex dump
 *
 * @author Brian Wellington
 */
public class hexdump {

  private static final char[] hex = "0123456789ABCDEF".toCharArray();

  /**
   * Dumps a byte array into hex format.
   *
   * @param description If not null, a description of the data.
   * @param b The data to be printed.
   * @param offset The start of the data in the array.
   * @param length The length of the data in the array.
   */
  public static String dump(String description, byte[] b, int offset, int length) {
    StringBuilder sb = new StringBuilder();

    sb.append(length).append("b");
    if (description != null) {
      sb.append(" (").append(description).append(")");
    }
    sb.append(':');

    int prefixlen = sb.toString().length();
    prefixlen = (prefixlen + 8) & ~7;
    sb.append('\t');

    int perline = (80 - prefixlen) / 3;
    for (int i = 0; i < length; i++) {
      if (i != 0 && i % perline == 0) {
        sb.append('\n');
        for (int j = 0; j < prefixlen / 8; j++) {
          sb.append('\t');
        }
      }
      int value = (int) b[i + offset] & 0xFF;
      sb.append(hex[value >> 4]);
      sb.append(hex[value & 0xF]);
      sb.append(' ');
    }
    sb.append('\n');
    return sb.toString();
  }

  public static String dump(String s, byte[] b) {
    return dump(s, b, 0, b.length);
  }
}
